Including parameters when defining a class's member functions is returning an error

I have the following class definition, written in C++, residing in it's own header file (ManageFeed.h)

#include <string>
#include <fstream>
#include <iostream>
#include <cstring>

class ManageFeed
{
    bool get_feed();
    void format_feed();
    bool refresh_feed();
    int find_start_of_string(string tag, ifstream& rssfile);
public:
    void display_feed_list();
    void display_feed_item();
    ManageFeed();
};

When I try to compile this code, I get the following error

custom-headers/ManageFeed.h:22: error: ‘string’ has not been declared
custom-headers/ManageFeed.h:22: error: ‘ifstream’ has not been declared

I find that I can successfully compile the code without any errors if I remove the parameters from the int find_start_of_string() function, but aren't the parameters required if data is to be passed into the function? If I try to call this function from main(), I receive the following error

reader.cpp:6: error: prototype for ‘void ManageF开发者_运维知识库eed::find_start_of_string(std::string, std::ifstream&)’ does not match any in class ‘ManageFeed’

so they are clearly required for the function to be usable. The textbook I'm using has examples of class definitions in their own head files with parameters present, but there seems to be no other difference in the structure of my code, nor is there any explanation given for why the books code works and mine doesn't.

Question: Are the parameters not required in the definition (the function definitions in ManageFeed.cpp have parameters specified) or am I doing something wrong here?

If anybody's interested, here's my application file

#include "custom-headers/ManageFeed.h"
using namespace std;

ifstream rssfile; 
const string tag;
void ManageFeed::find_start_of_string(string tag, ifstream& rssfile);

int main()
{ 
      ManageFeed manage_example;
      rssfile.open("rss.xml");
      manage_example.find_start_of_string(tag, rssfile);

     return 0;
}

and the implementation file for ManageFeed

#include "ManageFeed.h"

#include <iostream>
#include <string>
#include <cstring>

ManageFeed::ManageFeed()
{
}

/*
    A function that will get the location of the RSS file from the user
*/
bool ManageFeed::get_feed()
{
cout << "Please specify the location of the feed: " << endl << endl;
cin >> feed_source;
return true;
}

 void ManageFeed::store_feed()
{
ifstream source_feed;
source_feed.open(feed_source);

ifstream local_feed;
local_feed.open
(
    "/../File System/Feed Source Files/Example Feed/Example Feed.xml"
);
local_feed << source_feed;
 }

 int ManageFeed::find_start_of_string(string tag, ifstream& rssfile)
 {
bool return_value = false;
string line;
size_t found;
do
{
    getline(rssfile, line, '\n');
    found = line.find(tag);
    if (found != string::npos)
    {
        return_value = true;
        return found;
    }
} while (!return_value && !rssfile.eof());

if (!return_value)
{
}
}

---

John has the right solution. Here is the reasoning.

Both string and ifstream live in a namespace called std. When you say string you are telling the compiler to look into the global namespace and find a token called string. There is no such thing. You have to tell the compiler where to find string.

To do so you can either prefix them with std::string and std::ifstream or you can add using namesapce std; at the top of your header file.

Looking a little more closely, you do have the using directive in you .cpp file, but you put it after you include the header. That means the compiler parses the header without the namespace and then parses the rest of the file with it. If you just move the using directive above the header include, it will also fix your problem. Note, however, that anything else using the header will also need to do that same. Thus, start your .cpp file this way:

using namespace std;
#include "custom-headers/ManageFeed.h"

---

Change:

int find_start_of_string(string tag, ifstream& rssfile);

to:

int find_start_of_string(std::string tag, std::ifstream& rssfile);

Aside: why were there so many questions just like this one today?